Stainless steel sheet coated with a self-cleaning coating

Abstract

The invention has as an object a stainless steel sheet coated with a coating comprising, in the order starting from the surface of the said sheet: a barrier layer of metallic oxide or oxy-hydroxide MO x , or of metallic nitride or oxy-nitride NM x , having a thickness ranging between 5 and 1000 nm, a porous layer of titanium oxide TiO x having a thickness ranging between 5 and 1000 nm, the said TiO x layer having a voluminal porosity ranging between 10 and 50% and a mean pore size ranging between 0.5 and 100 nm and an upper layer of silicon oxide or oxy-hydroxide SiO x having a thickness ranging between 5 and 1000 nm. The invention also relates to the method for manufacture of this coated sheet.

1 . Stainless steel sheet coated on at least one of its faces with a coating comprising, in the order starting from the surface of the said sheet:
 a barrier layer of metallic oxide or oxy-hydroxide MO x , or of metallic nitride or oxy-nitride NM x , having a thickness ranging between 5 and 1000 nm,   a porous layer of titanium oxide TiO x  having a thickness ranging between 5 and 1000 nm, the said TiO x  layer having an RMS roughness ranging between 0.5 and 50 nm, a voluminal porosity ranging between 10 and 50% and a mean pore size ranging between 0.5 and 100 nm.   
   
   
       2 . Sheet according to  claim 1 , characterized in that the RMS roughness of the said porous layer of TiO x  ranges between 1 and 20 nm. 
   
   
       3 . Stainless steel sheet coated on at least one of its faces with a coating comprising, in the order starting from the surface of the said sheet:
 a barrier layer of metallic oxide or oxy-hydroxide MO x , or of metallic nitride or oxy-nitride NM x , having a thickness ranging between 5 and 1000 nm,   a porous layer of titanium oxide TiO x  having a thickness ranging between 5 and 1000 nm, the said TiO x  layer having a voluminal porosity ranging between 10 and 50% and a mean pore size ranging between 0.5 and 100 nm, and   an upper layer of silicon oxide or oxy-hydroxide SiO x  having a thickness ranging between 5 and 1000 nm.   
   
   
       4 . Sheet according to  claim 1 , characterized in that the thickness of the said porous layer of titanium oxide TiO x  ranges between 20 and 500 nm. 
   
   
       5 . Sheet according to  claim 4 , characterized in that the thickness of the said porous layer of TiO x  ranges between 30 and 200 nm. 
   
   
       6 . Sheet according to  claim 1 , characterized in that the voluminal porosity of the said porous layer of TiO x  ranges between 20 and 40%. 
   
   
       7 . Sheet according to  claim 1 , characterized in that the mean pore size of the said porous layer of TiO x  ranges between 1 and 20 nm. 
   
   
       8 . Sheet according to  claim 1 , characterized in that the said porous layer of titanium oxide TiO x  is a layer of titanium dioxide TiO 2 . 
   
   
       9 . Sheet according to  claim 8 , characterized in that the titanium dioxide TiO 2  is in its anatase crystalline form. 
   
   
       10 . Sheet according to  claim 3 , characterized in that the thickness of the said upper layer of silicon oxide or oxy-hydroxide SiO x  ranges between 20 and 850 nm. 
   
   
       11 . Sheet according to  claim 3 , characterized in that the said upper layer of silicon oxide is a layer of silicon dioxide SiO 2 . 
   
   
       12 . Sheet according to  claim 1 , characterized in that the thickness of the said barrier layer ranges between 20 and 850 nm. 
   
   
       13 . Sheet according to  claim 1 , characterized in that the said barrier layer of metallic oxide or oxy-hydroxide is chosen from among the oxides or oxy-hydroxides of silicon, tin, aluminum, alone or in combination. 
   
   
       14 . Sheet according to  claim 13 , characterized in that the said barrier layer is chosen from among SiO 2 , SnO 2 , Al 2 O 3 , alone or in combination. 
   
   
       15 . Sheet according to  claim 1 , characterized in that the said barrier layer of metallic nitride or oxy-nitride NM x  is a silicon nitride or oxy-nitride. 
   
   
       16 . Method for manufacture of a stainless steel sheet coated according to  claim 3 , comprising successive steps consisting in:
 depositing a barrier layer of metallic oxide or oxy-hydroxide MO x  or of metallic nitride or oxy-nitride NM x  on at least one of the faces of the said stainless steel sheet,   depositing, by a sol-gel method, a porous layer of titanium oxide TiO x  on the surface of the said barrier layer coating the stainless steel sheet, and depositing an upper layer of silicon oxide or oxy-hydroxide SiO x  on the said layer of titanium oxide TiO x .   
   
   
       17 . Method according to  claim 16 , characterized in that the said porous layer of TiO x  is formed by application on the said barrier layer of a polymeric sol comprising 0.1 to 0.6 mole/l of an organic precursor of titanium. 
   
   
       18 . Method according to  claim 17 , characterized in that the said organic precursor of titanium is a titanium alkoxide Ti(OR) 4 , in which R is an alkyl chain containing 1 to 4 carbon atoms. 
   
   
       19 . Method according to  claim 16 , characterized in that the said porous layer of TiO x  is formed by application on the said barrier layer of a crystalline suspension comprising 0.1 to 0.4 mole/l of nano-crystallites of titanium dioxide dispersed in a dispersive solvent. 
   
   
       20 . Method according to  claim 16 , characterized in that the said barrier layer is deposited by a sol-gel method. 
   
   
       21 . Method according to  claim 20 , characterized in that the said barrier layer of MO x  is formed by application, to at least one of the faces of the said sheet, of a polymeric sol comprising 0.2 to 2 mole/l of at least one precursor chosen from among an organometallic compound and a metallic salt. 
   
   
       22 . Method according to  claim 21 , characterized in that the said organometallic compound is a metal alkoxide M(OR) 3  or M(OR) 4 , in which the metal M is silicon, aluminum or tin, and R is an alkyl chain containing 1 to 4 carbon atoms. 
   
   
       23 . Method according to  claim 21 , characterized in that the said metallic salt is a nitrate or a chloride of silicon, aluminum or tin. 
   
   
       24 . Method according to  claim 16 , characterized in that the said upper layer of silicon oxide or oxy-hydroxide SiO x  is deposited by a sol-gel method. 
   
   
       25 . Method according to  claim 24 , characterized in that the said upper layer of SiO x  is formed by application on the said TiO x  layer of a polymeric sol comprising 0.2 to 2 mole/l of an organometallic precursor of silicon. 
   
   
       26 . Method according to  claim 25 , characterized in that the said organometallic precursor of silicon is a silicon alkoxide Si(OR) 4 , in which R is an alkyl chain containing 1 to 4 carbon atoms. 
   
   
       27 . Equipment for the food-processing industry made from a stainless steel sheet coated according to  claim 3 . 
   
   
       28 . Prefabricated section for a building made from a stainless steel sheet coated according to  claim 3 . 
   
   
       29 . Use of the stainless steel sheet according to  claim 3  in order to remove, through washing with water, the dirt adhering to the said coating without its being necessary to add a detergent to the water, and without its being necessary to subject the said sheet to a UV radiation or to a visible luminous radiation. 
   
   
       30 . The sheet according to  claim 3 , wherein the thickness of the said porous layer of titanium oxide TiO x  ranges between 20 and 500 nm. 
   
   
       31 . The sheet according to  claim 30 , wherein the thickness of the said porous layer of TiO x  ranges between 30 and 200 nm. 
   
   
       32 . The sheet according to  claim 3 , wherein the voluminal porosity of the said porous layer of TiO x  ranges between 20 and 40%. 
   
   
       33 . The sheet according to  claim 3 , wherein the mean pore size of the said porous layer of TiO x  ranges between 1 and 20 nm. 
   
   
       34 . The sheet according to  claim 3 , wherein said porous layer of titanium oxide TiO x  is a layer of titanium dioxide TiO 2 . 
   
   
       35 . The sheet according to  claim 34 , wherein the titanium dioxide TiO 2  is in its anatase crystalline form. 
   
   
       36 . The sheet according to  claim 3 , wherein the thickness of the said barrier layer ranges between 20 and 850 nm. 
   
   
       37 . The sheet according to  claim 3 , said barrier layer of metallic oxide or oxy-hydroxide is chosen from among the oxides or oxy-hydroxides of silicon, tin, aluminum, alone or in combination. 
   
   
       38 . The sheet according to  claim 38 , wherein said barrier layer is chosen from among SiO 2 , SnO 2 , Al 2 O 3 , alone or in combination. 
   
   
       39 . The sheet according to  claim 3 , wherein said barrier layer of metallic nitride or oxy-nitride NM x  is a silicon nitride or oxy-nitride.